In the conventional field of stereolithography and rapid prototyping apparatus, three-dimensional objects are build by layer-wise solidification of a material solidifyable under the action of electromagnetic radiation, commonly by photo-hardening of a photopolymer. There are methods and devices for the layered-wise construction of three-dimensional objects by exposure through an imaging unit comprising a predetermined number of discrete elements (pixels). Reference can be made, for example, to U.S. Pat. No. 5,247,180, U.S. Pat. No. 5,980,813, DE 93 19 405.5 U, DE 299 11 122 U, EP 1 250 995 A, EP 1 338 846 A, WO 01/00390, and WO 2005/110722.
With laser-based systems for photo-polymerisation, the energy or light output in the exposure point is provided by energy setting of the laser beam. To selectively harden a corresponding layer, the laser beam is scanned over the cross-sectional surface to be correspondingly hardened. The contours of the cross-sectional surface to be hardened can be scanned by the laser beam as a curve.
The layer-wise building of the three-dimensional object occurs by solidification in a cross-sectional area corresponding to a cross-section of a three-dimensional (3D) model corresponding to the three-dimensional object. Thus, the cross-sectional area to be hardened lies in the XY building plane and respective layers are hardened to a desired layer thickness in the Z dimension (Z direction). For execution of this building method, a process includes a step of slicing 3D model data (STL) into a group of sliced two-dimensional (2D) data to correspond to the cross-sectional area to be exposed. This prior art is illustrated schematically in FIG. 1.
The afore-mentioned prior art transformation of 3D model data to sliced, layered 2D data corresponding to respective cross-sectional areas, however, is complex and involve extensive algorithms and computer processing. Furthermore, accuracy of a layer-wise hardening of a photo-polymer depends on numerous factors, such as apportionment of the sliced cross-sections according to Z heights, setting of the contour lines of the sliced cross-sectional areas and a corresponding adjustment of an energy (light output) source and respective control elements, etc.